According to the scenario analysis (for 2010) with the assessment made by International Energy Agency (IEA), for mitigating the greenhouse effect by maintaining the rise of the global temperature at 2 celsius degrees (° C.) until 2050 (2 Degree Scenario, 2DS), CO2 capture and storage (CCS) is one of the most effective carbon reduction technologies with a 14-percents (%) carbon reduction contribution. Capturing CO2 from stationary sources, such as coal (gas)-fired power plants, petrochemical plants, cement plants, steel mills, is the most effective CO2 reduction technology. These sources will make CO2 emissions having high concentrations. After evaluating the CO2 capture technologies (such as alkanolamine) for post-combustion by U.S. NETL, about 30% of power consumption is figured out, which is much higher, about 10%, than that of CO2 capture technologies for pre-combustion. Hence, developing solid-state CO2 sorbents for the latter technologies would gain environmental benefits. For example, Patent US 20120025134 A1 synthesizes calcium oxide/magnesium oxide (CaO/MgO) to maintain CO2 conversion more than 90% at 800˜900° C. for 600 minutes (min) (under 15% of CO2). Another prior art uses metal oxide, such as CaO, for CO2 capture, which removes 99˜100% of CO2 at 650° C. (under 13˜16% of CO2). The above high-temperature CO2 sorbents is used under CO2 concentration less than 16%. However, with the same mass of gas, CO2 capture under a concentration of 40˜50% is more effective than that under 8˜15%.
In summary, disadvantages of the prior arts include:
1. The CO2 sorbents made with solvents through wet scrubbing and amine modification are used for lower CO2 concentrations around 5˜15% under low temperature around 20˜150° C. These CO2 sorbents have characteristics of big energy penalty, high regeneration energy, small carbon capacity and environmental harming.
2. Powders of natural CaO-containing minerals, like limestone (limestone), calcium carbonate (CaCO3) and serpentine, have poor stability. When they are used for capturing CO2 under medium-high temperature, the CO2 concentration should be less than 10% and the applications are for post-combustion. If they are used for pre-combustion (under 15˜40% of CO2), stability becomes poor and performance of CO2 capture rapidly declines.
3. The powders of synthesized CO2 sorbents are prone to problems of aggregation and structural embrittlement while being used for capturing CO2 at medium-high temperature under high steam and high CO2 concentration. Therefore, their characteristics on CO2 capture cannot be acquired in reactors and a proper granulation technology is required to enhance their mechanical strength and stability.
Hence, the prior arts do not fulfill all users' requests on actual use.